(1) Field of the Invention
The present invention relates to an improvement in a carbonated drink bottle formed of a biaxially stretched polyester. More particularly, the present invention relates to a polyester bottle for a carbonated drink, in which the speed of transfer of carbon dioxide gas from the liquid phase of the drink to the gas phase at the time of opening the bottle is controlled to a very low level.
(2) Description of the Prior Art
A polyethylene terephthalate bottle formed by biaxial draw-blow molding has a much lighter weight than that of a glass bottle, and as described in the specification of U.S. Pat. No. 3,733,309, this bottle is excellent in the pressure resistance, rigidity and transparency and since the bottle has a much reduced permeability of gases such as oxygen and carbon dioxide gas, it is excellent in the content-preserving property. By virtue of these excellent properties, this polyester bottle is widely used as a vessel for preserving a carbonated drink.
Although this polyester bottle for a carbonated drink has the above-mentioned advantages not attained by ordinary glass bottles, it has recently been found that this polyester bottle has a certain defect not observed in glass bottles. More specifically, in a bottle product obtained by filling a carbonated drink into a polyester bottle and effecting sealing between the bottle and a cap, when the bottle is opened, carbon dioxide gas dissolved in the liquid phase of the drink is abruptly transferred to the gas phase and the cap being removed for opening is caused to fly out, that is, the so-called cap missile phenomenon takes place. In case of a bottled drink product having a large volume, a part of the packed drink is often taken out in small quantities and the bottle is sealed again by the cap. Also in this case, since carbon dioxide gas is transferred into the gas phase from the liquid phase of the drink at the time of opening, the concentration of carbon dioxide gas in the drink is drastically reduced to render the drink vapid and degrade the taste of the drink.